Compressed air drying unit

ABSTRACT

An air drying unit for compressed air systems is provided. The air drying unit has a precooler/reheater, a main cooler and a moisture separator. Incoming air is cooled to cause moisture within the compressed air to condense, which is then separated to dry the compressed air. The precooler/reheater, main cooler and moisture separator are designed as an integral unit that does not require pipes to connect the components together. Instead, compressed air flows through the sealed unit through passages therein between the precooler/reheater, main cooler and moisture separator.

BACKGROUND

The present inventions relate generally to industrial air dryers forcompressed air systems.

Compressed air is commonly used in factories to power pneumatic toolsand to blow air onto various surfaces for cleaning, expanding bags,moving parts, etc. Typically, factories have a centralized compressedair system installed that feeds a network of compressed air piping thatsupplies numerous tools or stations with compressed air. Thus, one ormore centralized air compressors may be used to supply an entire factoryspace with compressed air.

However, it is known that air compressors which draw air from thesurrounding atmosphere also introduce moisture into the compressed airfrom the water vapor naturally contained in atmospheric air. Moisturewithin compressed air used in factories can cause numerous problems. Forexample, in the case of power tools that use compressed air as a powersource, moisture within the supplied compressed air can cause corrosionof the internal components of the tool. In addition, where compressedair is blown onto surfaces, any moisture within the compressed air willalso be blown onto the surface along with the blown air. This can beparticularly problematic where it is a requirement that the surfaceremain dry, such as food packaging operations, and can also be a problemwith delicate surfaces that might be damaged by water particles withinthe compressed air.

Due to the problems associated with moisture within compressed airsystems, various types of air drying systems may be used in industrialfactories to remove moisture contained within compressed air. While suchsystems are useful and adequately address the potential problemsassociated with moisture in compressed air, such systems can be large insize and are not always effective in matching the required compressedair demand. Thus, it would be desirable to provide improved air dryingsystems for industrial factories, including small and large applicationswhere dried compressed air is needed.

SUMMARY

An air drying unit for compressed air systems is described. The airdrying unit includes a precooler/reheater that cools compressed airflowing in from an air inlet and warms compressed air flowing out of anair outlet. The precooled air flows from the precooler/reheater to amain cooler which cools the compressed air with a coolant. Moisturewhich condenses from the compressed air due to cooling thereof isseparated from the compressed air by a moisture separator to dry thecompressed air. The dried air then flows back through theprecooler/reheater to warm the compressed air before flowing out throughthe air outlet. The invention may also include any other aspectdescribed below in the written description or in the attached drawingsand any combinations thereof.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

The invention may be more fully understood by reading the followingdescription in conjunction with the drawings, in which:

FIG. 1 is a perspective view of an air drying unit;

FIG. 2 is another perspective view of the air drying unit from thereverse side;

FIG. 3 is a schematic view of the air drying unit showing compressed airflow through passages within the air drying unit;

FIG. 4 is a perspective view of multiple air drying units connectedtogether;

FIG. 5A is an exploded view of a clamp; and

FIG. 5B is a cross section of a portion of the clamp of FIG. 5A.

DETAILED DESCRIPTION

Referring now to the figures, an air drying unit 10 is provided withthree main components. That is, the air drying unit 10 has aprecooler/reheater 12, a main cooler 14 and a moisture separator 16. Inoperation, compressed air from the air inlet 18 enters the precoolerside 12A of the precooler/reheater 12. The air then exits theprecooler/reheater 12 and enters the main cooler 14. After cooling thecompressed air, the air enters the moisture separator 16. The moistureseparator 16 may be within the main cooler 14 or may be a separatecomponent located after the main cooler 14. The air then reenters theprecooler/reheater 12 on the reheater side 12B, and thereafter, exitsthe air drying unit 10 through the air outlet 20.

The precooler/reheater 12 is a heat exchanger 12 that exchanges heatbetween the incoming air flow and the outgoing air flow. That is, theincoming compressed air flow is warm relative to the outgoing compressedair flow. As described below, the air is cooled within the drying unit10 to withdraw moisture from the air. Thus, the precooler/reheater 12increases efficiency by cooling the incoming air with the outgoing airprior to additional cooling that occurs thereafter. Also, it isundesirable for the outgoing air to be too cool since this would coolthe compressed air piping and cause condensation of water vapor on theexterior of the piping. Thus, the precooler/reheater 12 prevents thisfrom happening by heating the outgoing compressed air using the warmincoming compressed air. The energy required to cool the compressed airin the main cooler 14 is also reduced. It is also possible to reduce thesize of the main cooler 14 due to the precooling that is done to thecompressed air.

The main cooler 14 is another heat exchanger 14 that performs theprimary cooling of the compressed air. Cooling of the incomingcompressed air by the main cooler 14 is necessary in order to causegaseous moisture (i.e., humidity) within the air to condense to a fluid(e.g., water) in order to allow the moisture to be removed from the air.The main cooler 14 (which may be referred to as a chiller section) maycool the compressed air in various ways. In one embodiment, the maincooler 14 may use a liquid coolant, such as a glycol and water mixture,to cool the compressed air. In this case, the main cooler 14 is aliquid-air heat exchanger 14. Alternatively, the main cooler 14 may usea refrigerant to cool the compressed air. Thus, in this case, therefrigerant side of the main cooler 14 may be considered to be anevaporator where the refrigerant evaporates and absorbs heat from thecompressed air side of the main cooler 14. It is also possible to havemain coolers 14 that utilize a liquid coolant and a refrigerant.

After the incoming compressed air has been cooled by the main cooler 14(e.g., to below 5° C. and as low as 0° C.), the moisture separator 16withdraws moisture from the compressed air. In the preferred embodiment,the moisture separator 16 is located below the main cooler 14. Thus,gravity may be used to allow the condensed fluid to be removed through adrain 22. In this arrangement, the compressed air which has been driedby removing moisture therefrom (and which may now be considered theoutgoing compressed air) may change direction, e.g., a U-turn, and flowupwards from the moisture separator 16. It is understood that wheremultiple drying units 10 are used together, the drains 22 of the units10 may be connected together to provide a single drain system.

The outgoing compressed air then enters the reheater side 12B of theprecooler/reheater 12 and exits the drying unit 10 through the airoutlet 20. It is understood that air flow through the air drying unit 10need not be separately forced or circulated therethrough, but insteadmay flow through the drying unit 10 as air is used by the compressed airdemand and replaced by the compressed air supply. That is, anycompressed air that flows to the compressed air demand from thecompressed air supply must first pass through the drying unit 10 (oranother drying unit 10 in the system) due to the location of the dryingunit 10 between the supply and demand.

The drying unit 10 is designed to be compact and an integral unit. Thus,the unit 10 may be smaller than other conventional air dryers withequivalent capacity. That is, the precooler/reheater 12, main cooler 14and moisture separator 16 are all interconnected together in a unit 10without being connected together with pipes and pipe couplers orfasteners. Instead, air flows between the precooler/reheater 12, maincooler 14 and moisture separator 16 through internal passages 24 withinthe drying unit 10. In order to contain the air within the unit 10, itis necessary to ensure that the unit 10 is sealed sufficiently tocontain compressed air (e.g., 100-200 psi). While the unit 10 may bemade as a monolithic unit incorporating the precooler/reheater 12, maincooler 14 and moisture separator 16, it may be preferred that thecomponents be welded (e.g., brazed) together so that the components arepermanently connected together in sealed together (i.e., the internalpassages 24 are sealed by the welds). For example, theprecooler/reheater 12 may be welded 26 to the main cooler 14 and may bewelded 28 to the moisture separator 16. The main cooler 14 may also bewelded 30 to the moisture separator 16.

In order to make the drying unit 10 vertically compact, it may bedesirable to partially overlap the precooler/reheater 12 vertically withthe main cooler 14. That is, the bottom end of the precooler/reheater 12may be laterally adjacent the top end of the main cooler 14. A moretraditional arrangement would be to arrange the precooler/reheater 12 ontop of the main cooler 14 so that the incoming compressed air flowsdownward from the precooler/reheater 12 to the main cooler 14. However,in the preferred embodiment, the precooler/reheater 12 and main cooler14 are offset from each other and partially overlapping in aside-by-side arrangement so that the incoming compressed air changesdirection at the end of the precooler/reheater 12 to flow laterally fromthe precooler/reheater 12 to enter the main cooler 14. As a result, theheight of the drying unit 10 can be reduced.

In order to make the drying unit 10 modular and more easily used withmultiple drying units 10 as described further below, the air inlet 18and air outlet 20 may be pipes 18, 20 extending across the width of theunit 10. In this arrangement, the axes of the pipes 18, 20 (which extendparallel to each other) extend in one direction across the unit 10, butthe compressed air must flow laterally with respect to the pipe axes inorder to enter and exit the drying unit 10. This may be accomplished bycutting a side opening through each pipe 18, 20 to fit the pipe 18, 20against the drying unit 10 and welding 32 the pipe 18, 20 to the dryingunit 10. Thus, the compressed air flows laterally from or to therespective pipe 18, 20 to enter and exit the drying unit 10. Theopenings 34 at the opposite ends of the pipes 18, 20 may be used toconnect the drying unit 10 to the compressed air supply and compressedair demand. Preferably, the inlet pipe 18 and the outlet pipe 20 haveequal lengths and are preferably longitudinally aligned with each otherso that the end openings 34 of the two pipes 18, 20 extend out from thedrying unit 10 the same length. It may be desirable to close one end 34of each pipe 18, 20 with a plug or cap 36 when an additional drying unit10 is not connected to the unit 10. It is understood that the inlet andoutlet pipes 18, 20 could be connected to the compressed air system ofthe facility on the same side of the drying unit 10 or on opposite sidesas desired. It may also be desirable to provide pressure measurementtaps in the air inlet and outlet pipes 18, 20 to measure pressure dropacross the drying unit 10.

A similar arrangement may be used for the coolant pipes 38, 40 as well.The inlet 38 and outlet 40 coolant pipes allow the coolant to flow intoand out of the main cooler 14. Preferably, the coolant pipes 38, 40 arecut and shaped to the side of the main cooler 14 and are welded 42 tothe main cooler 14. Like the air inlet and outlet pipes 18, 20, thecoolant flows laterally from the respective pipe 38, 40 to enter andexit the main cooler 14. The coolant pipes 38, 40 are also preferablythe same length and aligned with each other so that the end openings 44of the two pipes 38, 40 extend out from the drying unit 10 the samelength. It is understood that various arrangements may be used for thecoolant pipes 38, 40 depending on the particular application anddepending on whether a liquid coolant or a refrigerant is used.

One advantage of the drying unit 10 is that it may be chained togetherwith multiple drying units 10 to increase capacity. It is understoodthat because the air drying units 10 have a common design manufacturingthe units 10 may be more efficient. Also, performing maintenance on theunits 10 in operation may be easier due to their commonality. Becauseadding each additional unit 10 increases capacity in an additivefashion, compressed air demand can also be matched more closely andcapacity may be added to a factory at a later time if needed merely beadding additional drying units 10.

By connecting the air inlet pipes and air outlet pipes of multipledrying units 10 together, the drying units 10 are arranged in parallelwith each other between the compressed air supply and the compressed airdemand. In other words, when multiple air drying units 10 are connectedtogether and operating simultaneously, the compressed air flow from thesupply is split into separate portions that flow through separate dryingunits 10. Thus, where there are two drying units 10 connected together,the compressed air flow will be divided in half due to the pressuredifferences so that half the compressed air flows from the air inlets 18through each drying unit 10. The portions are then recombined at the airoutlets 20 after flowing through the multiple drying units 12 in orderto be supplied to the compressed air demand. Therefore, by connectingthe air inlet pipes 18 together and the air outlet pipes 20 together ofmultiple units 10, the connected pipes 18, 20 act as a common inletheader and a common outlet header. The air inlet and outlet pipes 18, 20can be connected to a coupling or fitting, such as a tee, elbow orstraight pipe section which may act as a central pipe carryingcompressed air to the assembly. The tee, elbow or straight pipe may beused to connect to the compressed air system of the facility. An inletfilter and/or outlet filter with the same type of grooved connection orflanged connection may also be connected to the drying unit 10 assemblyto filter the compressed air entering and exiting the assembly.

The air inlet pipes 18 and the air outlet pipes 20 are preferably eachconnected together with a clamp 46 that wraps around the ends 34 of twoadjacent pipes 18, 20. Thus, the units 10 are not connected togetherwith intervening pipes, but are located directly adjacent each otherwith a single clamp 46 connecting two adjacent pipe ends 34 together. Asshown in FIGS. 5A-5B, the clamps 46 may have rigid (e.g., metal) halfround clamp members 52 with a circular groove 56 therein. A flexibleround seal (e.g., plastic) 54 may be located in the central groove 56 ofthe clamp members 52. The seal 54 may have ends 58 that are pressed intocorresponding grooves 60 in the air inlet and outlet pipes 18, 20. Bolts62 and nuts 64 may be used to tighten the two clamp members 52 togetherand squeeze the seal 54 against the ends 34 of the pipes 18, 20.

A similar connection may be made with the coolant inlet pipes 38 and thecoolant outlet pipes 40. Thus, the coolant pipes 38, 40 may be directlyconnected to corresponding adjacent coolant pipes 38, 40 with a pipecoupler (e.g., a swivel connector) without intervening pipes. Likedescribed above, this results in the coolant pipes 38, 40 acting ascommon headers where the coolant is split evenly between the maincoolers 14 of the units 10 so that equal portions flow from the coolantinlet pipes 38 into the main coolers 14, and the coolant is recombinedin the coolant outlet pipes 40 after flowing through the main coolers14. This arrangement would be particularly useful where a liquid coolantis used in contrast to a refrigerant which would preferably be feddirectly to each main cooler separately.

Therefore, it can be seen that the air drying units 10 can be easilyadded together to satisfying increased compressed air demand whileproviding a compact package and common design. In addition to connectingthe drying units 10 together with the pipes 18, 20, 38, 40 andconnecting fasteners 46, 48, it may also be desirable to provideadditional structural supports 50 that are connected to multiple dryingunits 10 to securely connect the units 10 together.

While preferred embodiments of the inventions have been described, itshould be understood that the inventions are not so limited, andmodifications may be made without departing from the inventions herein.While each embodiment described herein may refer only to certainfeatures and may not specifically refer to every feature described withrespect to other embodiments, it should be recognized that the featuresdescribed herein are interchangeable unless described otherwise, evenwhere no reference is made to a specific feature. It should also beunderstood that the advantages described above are not necessarily theonly advantages of the inventions, and it is not necessarily expectedthat all of the described advantages will be achieved with everyembodiment of the inventions. The scope of the inventions is defined bythe appended claims, and all devices and methods that come within themeaning of the claims, either literally or by equivalence, are intendedto be embraced therein.

The invention claimed is:
 1. An air drying unit for compressed air,comprising: a first pipe having a sidewall that defines a first openingand a second opening, the first opening opposite to the second opening,the first opening configured to receive incoming compressed air, thefirst pipe including an air inlet located on the sidewall between thefirst opening and the second opening; a second pipe having a sidewallthat defines a first opening and a second opening, the first openingopposite to the second opening, the second pipe including an air outletlocated on the sidewall between the first opening and the secondopening, the air outlet configured to receive outgoing compressed air; aprecooler/reheater connected to the air inlet and the air outlet, theprecooler/reheater being a first heat exchanger between incomingcompressed air from the air inlet and outgoing compressed air to the airoutlet, wherein the incoming compressed air is cooled by the outgoingcompressed air and the outgoing compressed air is warmed by the incomingcompressed air, the sidewall of the first pipe and the sidewall of thesecond pipe directly coupled to the precooler/reheater; a main coolerconnected to the precooler/reheater such that the incoming compressedair enters the main cooler after exiting the precooler/reheater, themain cooler being a second heat exchanger between the incomingcompressed air and a coolant, wherein the coolant cools the incomingcompressed air and causes moisture to condense from the incomingcompressed air; and a moisture separator connected to the main cooler,the moisture separator separating the moisture from the incomingcompressed air, the incoming compressed air thereby being dried anddefining the outgoing compressed air, the outgoing compressed airentering the precooler/reheater from the main cooler and the moistureseparator; wherein the precooler/reheater, the main cooler and themoisture separator define a unit that is integral such that the incomingcompressed air and the outgoing compressed air flow through and betweenthe precooler/reheater, the main cooler and the moisture separatorthrough internal passages within the unit and the unit being sealed suchthat the incoming compressed air and the outgoing compressed air iscontained therein between the air inlet and the air outlet.
 2. The airdrying unit according to claim 1, wherein the precooler/reheater and themain cooler are offset and partially overlapping each other such thatthe incoming compressed air flows laterally from the precooler/reheaterto the main cooler.
 3. The air drying unit according to claim 2, whereinthe precooler/reheater is partially above the main cooler and the maincooler is offset along a lower side of the precooler/reheater.
 4. Theair drying unit according to claim 1, wherein the moisture separator isbelow the main cooler such that moisture is separated by gravity and theoutgoing compressed air changes direction to flow upward from themoisture separator to the precooler/reheater.
 5. The air drying unitaccording to claim 1, wherein the precooler/reheater is welded to themain cooler.
 6. The air drying unit according to claim 1, wherein themoisture separator is welded to the main cooler and welded to theprecooler/reheater.
 7. The air drying unit according to claim 1, whereinat least one of the first pipe or the second pipe are welded to theprecooler/reheater.
 8. The air drying unit according to claim 1, whereinthe first opening of the first pipe and the first opening of the secondpipe are aligned with each other and the second opening of the firstpipe and the second opening of the second pipe are aligned with eachother.
 9. The air drying unit according to claim 1, wherein the maincooler comprises a coolant inlet pipe with an opening at each end of thecoolant inlet pipe, the coolant flowing laterally from the coolant inletpipe to the main cooler.
 10. The air drying unit according to claim 9,wherein the coolant inlet pipe is welded to the main cooler.
 11. The airdrying unit according to claim 9, wherein the main cooler comprises acoolant outlet pipe with an opening at each end of the coolant outletpipe, the coolant flowing laterally to the coolant outlet pipe from themain cooler.
 12. The air drying unit according to claim 11, wherein thecoolant outlet pipe is welded to the main cooler.
 13. Two of the airdrying unit according to claim 1, further comprising a first clampconfigured to couple the first pipes of the two air drying unitstogether and a second clamp configured to couple the second pipes of thetwo air drying units together; wherein air flowing through the firstpipes flows evenly into the air inlets of the two air drying units andair flowing through the second pipes flows evenly into the second pipesfrom the air outlets of the two air drying units.
 14. The two of the airdrying unit according to claim 13, wherein the first and second clampseach comprise two rigid half round clamp members and a flexible sealdisposed within the clamp members.
 15. The two of the air drying unitaccording to claim 14, wherein the flexible seal is disposed within agroove in the end of each of the first and second pipes.
 16. The two ofthe air drying unit according to claim 13, wherein the main cooler ofeach air drying unit comprises a coolant inlet pipe with an opening ateach end of the coolant inlet pipe, the coolant flowing laterally fromthe coolant inlet pipes to the respective main cooler, and the ends ofthe coolant inlet pipes being connected to each other, the coolantflowing evenly from the coolant inlet pipes into the main coolers of thetwo air drying units.
 17. The two of the air drying unit according toclaim 16, wherein the main cooler of each air drying unit comprises acoolant outlet pipe with an opening at each end of the coolant outletpipe, the coolant flowing laterally to the coolant outlet pipes from therespective main cooler, and the ends of the coolant outlet pipes beingconnected to each other, the coolant flowing evenly into the coolantoutlet pipes from the main coolers of the two air drying units.
 18. Anair drying unit for compressed air, comprising: an air inlet and an airoutlet; a precooler/reheater connected to the air inlet and the airoutlet, the precooler/reheater being a first heat exchanger betweenincoming compressed air from the air inlet and outgoing compressed airto the air outlet, wherein the incoming compressed air is cooled by theoutgoing compressed air and the outgoing compressed air is warmed by theincoming compressed air; a main cooler connected to theprecooler/reheater such that the incoming compressed air enters the maincooler after exiting the precooler/reheater, the main cooler being asecond heat exchanger between the incoming compressed air and a coolant,wherein the coolant cools the incoming compressed air and causesmoisture to condense from the incoming compressed air; a moistureseparator connected to the main cooler, the moisture separatorseparating the moisture from the incoming compressed air, the incomingcompressed air thereby being dried and defining the outgoing compressedair, the outgoing compressed air entering the precooler/reheater fromthe main cooler and the moisture separator; a coolant inlet pipe havinga sidewall that defines a first opening and a second opening, the firstopening opposite to the second opening, the first opening configured toreceive incoming coolant, the first coolant pipe including an inletlocated on the sidewall between the first opening and the secondopening, the inlet fluidly coupled to the main cooler for supplying theincoming coolant, the sidewall of the coolant inlet pipe directlycoupled to the main cooler; and a coolant outlet pipe having a sidewallthat defines a first opening and a second opening, the first openingopposite to the second opening, the coolant outlet pipe including anoutlet located on the sidewall between the first opening and the secondopening, the outlet fluidly coupled to the main cooler for receivingoutgoing coolant, the sidewall of the second coolant pipe directlycoupled to the main cooler; wherein the precooler/reheater, the maincooler, and the moisture separator define a unit that is integral suchthat the incoming compressed air and the outgoing compressed air flowthrough and between the precooler/reheater, the main cooler, and themoisture separator through internal passages within the unit and theunit being sealed such that the incoming compressed air and the outgoingcompressed air is contained therein between the air inlet and the airoutlet.
 19. Two of the air drying unit according to claim 18, whereineach respective coolant inlet pipe of the two air drying units arefluidly coupled together, the incoming coolant flowing laterally fromeach coolant inlet to the respective main cooler.
 20. Two of the airdrying unit according to claim 18, wherein each respective coolantoutlet pipe of the two air drying units are fluidly coupled together,the outgoing coolant flowing laterally to each coolant outlet from therespective main cooler.